[Hallc] Reminder of /volatile usage

[Brad Sawatzky]

Hi all,

I had a brief exchange with a collaborator about how files were managed
on the /volatile file system.  Fortunately there were no problems in the
end (sounds like files had been managed correctly after all), but I
thought it might be a good time to send out a reminder on how /volatile
works.  Please read so you don't get surprised by having files removed
contrary to your expectations.

Files on /volatile are only *guaranteed* to persist for a few days,
after that the automatic pruning process described here kicks in,
removing files on a least-recently-used basis:
  https://scicomp.jlab.org/docs/volatile_disk_pool

If a (large) file needs to be kept for an extended period of time, then
it should go to tape and be managed using the jcache mechanisms.

Please do not make personal copies of files from /cache or other
tape-backed files systems into /volatile.  There is no need, and it
just increases the chance that legitimate files will be removed from
/volatile earlier than necessary.

Note this whole system works best if you manually delete files you know
are no longer needed rather than let the automated removal scripts do
their best.


** On a related note:  Supervisors should be asking their students how
   they are managing backups of analysis/simulation/thesis related files
   on their computers.
   --> Ask yourself/them how you would recover if you had a disk
       failure and lost all the data.  It happens more than you think.

Email me if you have questions and/or need support.

-- Brad

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov